Hi,
We are currently testing the performance with rbd caching enabled with
write-back mode on our openstack (grizzly) nova nodes. By default, nova fires
up the rbd volumes with "if=none" mode evidenced by the following cmd line from
"ps | grep".
-drive
file=rbd:ceph-openstack-volumes/volume-949e2e32-20c7-45cf-b41b-46951c78708b:id=ceph-openstack-volumes:key=12347I9RsEoIDBAAi2t+M6+7zMMZoMM+aasiog==:auth_supported=cephx\;none,if=none,id=drive-virtio-disk0,format=raw,serial=949e2e32-20c7-45cf-b41b-46951c78708b,cache=writeback
Does anyone know if this should be set to anything else (e.g., if=virtio
suggested by some qemu posts in general)? Given that the underline network
stack for RBD IO is provided by the linux kenerl instead, does this option bear
any relevance for rbd volume performance inside guest VM?
Thanks. --weiguo
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